Mix dry ingredients: In a bowl, whisk flour, baking powder, baking soda, and salt.
Cream butter + sugar: In a large bowl, beat butter, granulated sugar, and brown sugar until fluffy (2–3 minutes).
Add wet ingredients: Mix in eggs and vanilla until combined.
Combine dough: Add dry ingredients and mix just until a soft dough forms (don’t overmix).
Roll dough: Place dough between parchment paper and roll into a rectangle (about 10x14 inches).
Add filling: Spread softened butter over dough. Sprinkle brown sugar, cinnamon, and a pinch of salt evenly. Press lightly.
Roll into log: Roll tightly from the long side into a log. Wrap and chill for 1 hour.
Slice cookies: Cut into ½-inch slices.
Coat: Mix cinnamon sugar coating, then roll each slice lightly in it.
Bake: Place on lined baking sheet and bake at 350°F (175°C) for 9–11 minutes, until edges are set and centers look slightly soft.
Cool: Let cookies cool on the pan for 5 minutes, then move to a rack.
Optional glaze: Drizzle glaze over cooled cookies and let set.